https://github.com/hoglet67/RGBtoHDMI/wiki
Can't be used with the NES or SNES as-is, because the NES requires an extra stage for palette proxying, and both I think require fixing the missing pixel. Can't be used with the TG16 because it'll require palette proxying. But there are probably some other consoles that emit something easily used as input.
Currently achieved input bandwidth seems to be somewhere around 14MB/s, ish.